A federal judge on Tuesday revisited at a decades-old court settlement restricting how the New York Police Department conducts surveillance after civil rights lawyers accused the department of breaking those rules by monitoring Muslims.

The dispute centers on the restrictions set by the Handschu decree, which was put in place in response to surveillance used against war protesters in the 1960s and '70s. The decree was relaxed following the Sept. 11, 2001, terror attacks to allow police to more freely monitor political activity in public places.

"I've come to think of this case as a volcano that's asleep most of the time ... but every now and then blows up," U.S. District Judge Charles Haight said at the start of a hearing in federal court in Manhattan.